..Water parameters? Whats your ammonia, nitrite, nitrate, and temp? Size of tank, what type of filtration, how long has it been set up? Size of fish? Answers to these questions will help us determin the cause of the issues you're having.

Water looks pretty clean. I would suggest moving the fish to a qt tank if able. Treat with salt and add some maracyn2. What are u feeding the endli?
That’s a problem. It could easily get parasites or infection from the feeders.He has just been eating bloodworms an feeder fish
I'm going to add that stress from being harrassed also can cause the issue.
Tlindsey i did jus put those 2 redtail catfish in with him the day before....is there something i can do or will it go away on its own ?